[ovs-dev] [patch 0/2] datapath changes for 2.6.37-rc1

Jesse Gross jesse at nicira.com
Mon Jan 31 22:16:41 UTC 2011


On Sun, Jan 30, 2011 at 4:12 PM, Simon Horman <horms at verge.net.au> wrote:
> On Tue, Nov 02, 2010 at 01:11:40PM -0700, Jesse Gross wrote:
>> On Tue, Nov 2, 2010 at 5:35 AM, Simon Horman <horms at verge.net.au> wrote:
>> > Hi,
>> >
>> > The following two patches seem to be necessary and sufficient
>> > for the datapath to compile against 2.6.37-rc1.
>> >
>> > Lightly tested
>>
>> Both applied, thanks.
>>
>> There are a few things that I'm aware of that also should be taken
>> care of to be compatible with recent kernels.  They're a little more
>> subtle because they don't cause compilation problems:
>>
>> * RPS hash.  We should clear skb->rxhash when we make a modification
>> that could affect it.  This could come up in either actions like
>> changing the IP address or tunneling.
>>
>> * vlan acceleration.  In 2.6.37 we can start receiving packets with
>> vlan tags in the skb->vlan_tci field but we don't currently look for
>> them there.  We also need to take into account acceleration when
>> modifying/stripping a vlan tag.
>
> I am a little unclear on this. Or more to the point, I'm
> having a little trouble getting my mind around the VLAN implementation.

I can take care of this.  I actually started doing some work on this a
little while ago, so I'll just work on finishing that up.  Plus, I was
the one who made these changes upstream, I just haven't had time to do
it here.

>
> * I'm a little unclear how/when skb->vlan_tci is set on
>  the receive path.

If a NIC supports RX vlan acceleration, it will strip the tag off and
put it in skb->vlan_tci.

>
> * I am wondering how if we can get rid of some/all of
>  the special handling in modify_vlan_tci() for GSO and
>  the fact that Open vSwitch doesn't set a VLAN group.

Yes, this is one of the primary benefits of the change.  Previously
Open vSwitch couldn't take advantage of TSO with vlan packets, now it
can.




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